Search in Rotated Sorted Array leetcode java

题目：

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

题解：

这道题是一道常见的二分查找法的变体题。

要解决这道题，需要明确rotated sorted array的特性，那么就是至少有一侧是排好序的（无论pivot在哪，自己画看看）。接下来就只需要按照这个特性继续写下去就好。以下就以伪代码方法来说明：

如果target比A[mid]值要小
如果A[mid]右边有序（A[mid]<A[high])
那么target肯定不在右边（target比右边的都得小），在左边找
如果A[mid]左边有序
那么比较target和A[low]，如果target比A[low]还要小，证明target不在这一区，去右边找；反之，左边找。
如果target比A[mid]值要大
如果A[mid]左边有序（A[mid]>A[low]）
那么target肯定不在左边（target比左边的都得大），在右边找
如果A[mid]右边有序
那么比较target和A[high]，如果target比A[high]还要大，证明target不在这一区，去左边找；反之，右边找。

以上实现代码如下所示：

1    public int search(int [] A,int target){
2        if(A==null||A.length==0)
3          return -1;
4
5        int low = 0;
6        int high = A.length-1;
7
8        while(low <= high){
9            int mid = (low + high)/2;
10            if(target < A[mid]){
11                if(A[mid]<A[high])//right side is sorted
12                  high = mid - 1;//target must in left side
13                else
14                  if(target<A[low])//target<A[mid]&&target<A[low]==>means,target cannot be in [low,mid] since this side is sorted
15                     low = mid + 1;
16                  else
17                     high = mid - 1;
18            }else if(target > A[mid]){
19                if(A[low]<A[mid])//left side is sorted
20                  low = mid + 1;//target must in right side
21                else
22                  if(target>A[high])//right side is sorted. If target>A[high] means target is not in this side
23                     high = mid - 1;
24                  else
25                     low = mid + 1;
26            }else
27              return mid;
28        }
29
30        return -1;
31 }

Reference:http://www.cnblogs.com/ider/archive/2012/04/01/binary_search.html

转载于:https://www.cnblogs.com/springfor/p/3858140.html

Search in Rotated Sorted Array leetcode java相关推荐

leetcode 81 Search in Rotated Sorted Array II ----- java
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would this ...
Find Minimum in Rotated Sorted Array leetcode java
题目: Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 ...
LeetCode 33. Search in Rotated Sorted Array
问题链接 LeetCode 33. Search in Rotated Sorted Array 题目解析给定一个 "升序" 的无重复数组,从中寻找目标值."升序& ...
【leetcode】Search in Rotated Sorted Array II（middle）☆
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would this ...
LeetCode Search in Rotated Sorted Array II
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would t ...
LeetCode Search in Rotated Sorted Array II -- 有重复的旋转序列搜索
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would this ...
LeetCode Online Judge 题目C# 练习 - Search in Rotated Sorted Array II
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would this ...
leetcode - Search in Rotated Sorted Array II
Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would this ...
81. Search in Rotated Sorted Array II
题目: Follow up for "Search in Rotated Sorted Array": What if duplicates are allowed? Would ...
[算法题] Search in Rotated Sorted Array ii
题目内容题目来源:LeetCode Suppose an array sorted in ascending order is rotated at some pivot unknown to yo ...

Search in Rotated Sorted Array leetcode java

Search in Rotated Sorted Array leetcode java相关推荐

最新文章

热门文章